For those having trouble with 1-2:
Start putting a farmer down, then get 50 gold to put another down, THEN put another farmer. You will have 3 farmers and a goblin coming at you, don't worry since you will have the 100gold for archer soon. Put it on that lane, then put another archer on the other goblin coming and another farmer when you have the money.
By then, you will have 4 farmers and more than enough money to beat the level. There isn't a single level in this game you can't beat if you rush 4 farmers.